Growth Kinetics of Venous Tumor Thrombus from Renal Cell Carcinoma

Renal cell carcinoma (RCC) is known to form venous tumor thrombus (VTT); however, limited data exist on VTT growth rates. We sought to characterize the growth rate of VTT from RCC and identify clinicopathologic features associated with faster thrombus growth. Systemic therapy-naïve patients with RCC and VTT with 2 preoperative imaging studies performed with contrast at least 7 days apart were identified from a single institutional registry. VTT levels were assigned using the Mayo classification and measured in millimeters (mm). Changes between scans were linearized to growth rate per day. Multivariable regression models identified factors associated with VTT growth. We evaluated 141 patients with a median time between scans of 20 days (IQR: 12-30) and noted a median VTT growth rate of 0.3 mm/d. Sixteen (11%) patients were reclassified on the second scan to a higher Mayo VTT level. There was a significant relationship between VTT growth and increasing tumor thrombus level (P < .001) as well as the presence of sarcomatoid/rhabdoid features (0.4 vs 0.3 mm/d, P = .003). On multivariable regression, there is a quadratic increase in VTT growth rates as thrombus level increases (P = .001). Sarcomatoid/rhabdoid features (coefficient +0.43 mm/d, P < .001) and metastatic disease (coefficient +0.30 mm/d, P = .03) were also associated with increased tumor thrombus growth rates. VTT growth is generally less than 1 mm/d, although higher level thrombi and disease with aggressive histopathology grew more rapidly. These data improve the understanding of tumor thrombus growth and can aid in preoperative triage and surgical planning.